In recent years, the spotlight centers on the terrestrial environment and energy problems. In this situation, the transition to adoption of fuel battery with high energy density as a power source of portable devices has picked up momentum.
A general usage of the fuel battery is similar to that of well-known dry cells. Plural fuel batteries are serially connected, to produce a voltage necessary for a device, and the voltage is used as a power source. When the fuel is exhausted, a fuel cartridge tank is replaced with a new one, thereby power generation is started again.
This usage of serially-connected fuel batteries is very convenient, however, it has a problem that overvoltage occurs to each cell due to variation of performance of each battery cell and a problem that the stack (serial array) of the batteries itself does not function if the stack includes even one defective cell.
FIG. 7 is a block diagram showing a construction to solve these problems. In the figure, reference numeral 1 denotes a main power source (battery cell); 2, a booster converter; 3, a control circuit; and 4, a load. In this construction, since one booster converter 2 is provided for one battery cell 1, and the power source of the control circuit 3 is obtained from the main power source 1, a voltage necessary for the load 4 can be obtained without serially connecting batteries.
However, generally, the voltage generated per 1 fuel battery cell is merely about 0.7 V, therefore it is difficult to construct a control circuit which operates at this low voltage.
Further, as shown in FIG. 8 as an another example, the booster converter 2 may be provided with power storage means 5 on the secondary side, to obtain the power source of the control circuit 3 of the booster converter 2 from the power storage means 5.
However, in this method, as the load 4 is driven with the same power storage means 5, a large capacity battery or the like is required as the power storage means 5.